This project seeks to elucidate the neuroanatomical substrates of auditory communication in a reptile, the Tokay gecko. Electrophysiological techniques (multiple-unit recording and electrical stimulation of the brain) and experimental neuroanatomical techniques (autoradiography, HRP histochemistry, Fink-Heimer methods and 14C-2DG autoradiography) are employed to identify the neural regions and connections of the sensory component of auditory communication (auditory pathway) and those of its motor component (vocalization pathway). Attention is also directed toward identifying possible sites of interaction between these sensory and motor regions, using cytoarchitectural and neuromorphological methods. Sites of interaction must exist at some level in these two pathways, since such interactions unite the two pathways into the neural system which underlies auditory communication. The nonmammalian brain is often more suitable for the investigation of neural systems which are somewhat refractory to precise anatomical study in the mammalian brain. The Tokay gecko should be a valuable model for the analysis of the anatomy and organization of the neural pathways which mediate auditory communication, since both audition and vocalization are well developed in the gecko. The results of these investigations should provide insights into the organization of comparable systems in other vertebrates.